1. Technical Field
The present disclosure relates to semiconductor device fabrication and, more particularly, to an improved chemical mechanical polishing ("CMP") of a semiconductor wafer which results in a more efficient yield of in the manufacturing of semiconductor devices.
2. Description of the Related Art
Advances in electronic devices generally include reducing the size of the components that form integrated circuits. ICs, such as memory chips, logic devices, and the like. With smaller circuit components, the value of each unit area of a semiconductor wafer becomes higher. This is because the ability to use all of the wafer area for IC components improves. To properly form an IC that employs a much higher percentage of usable wafer area, it is critical that contaminant particle counts on the semiconductor wafer surface be reduced below levels which were previously acceptable. For example, minute particles of oxides and metals of less than 0.2 microns are unacceptable for many of the popular advanced circuit designs, because they can short out two or more conducting lines. In order to clean a semiconductor wafer and remove unwanted particles, a process known as chemical mechanical polishing ("CMP") has achieved widespread success.
Generally, CMP systems place a semiconductor wafer in contact with a polishing pad that moves relative to the semiconductor wafer. The semiconductor wafer may be stationary or it may also rotate on a carrier that holds the wafer. Between the semiconductor wafer and the polishing pad, CMP systems often use a slurry. The slurry is a liquid having the ability to lubricate the moving interface between the semiconductor wafer and the polishing pad while mildly abrading and polishing the semiconductor wafer surface with a polishing agent, such as silica or alumina.
During the CMP process, since the polishing pad contacts the semiconductor wafer, it is common for the polishing pad to eventually erode or wear unevenly across its surface. Therefore, the polishing pad must be conditioned periodically by a conditioning assembly. The conditioning assembly typically includes a plurality of diamonds on its conditioning surface and moves laterally across the polishing pad to uniformly condition the surface of the pad.
One of the fundamental problems associated with conventional CMP systems is the accumulation of particles and debris on the surface of the polishing pad which typically stem from the polishing process and the conditioning process. The particles and debris adversely affect the polishing process since they tend to scratch the surface of the semiconductor wafer and, like containments, can detrimentally affect operation of the resulting integrated circuit.
Another problem associated with conventional CMP systems is that the surface of the polishing pad may wear unevenly, since wafers are typically aligned in one position on the surface of the polishing pad, thereby detrimentally affecting the polishing uniformity. In an attempt to correct this problem, conventional pad conditioners incorporate the ability to move laterally across the surface of the pad. However, they do not have a means for adjusting the relative position of the conditioning elements with respect to the pad, to optimize the conditioning intensity.
Therefore, a need exists for an improved method and apparatus for conditioning a polishing pad of a CMP system which removes particles and debris from the surface of the pad and enables the optimization of the conditioning intensity.